IT Multisourcing (ITM), the provision of IT services by multiple interdependent vendors to a single client, is widely prevalent now. ITM, in principle, is believed to mitigate both strategic and operational risks of IT outsourcing for client organizations. Yet there is limited research which systematically investigates the effects of ITM on different forms of risk. This paper develops a theoretical framework to understand the implications of ITM for the specific risk of vendor opportunistic behaviour, classified as a 'strategic risk' of outsourcing. The fundamental attributes of ITM are identified and mechanisms through which they influence vendor opportunistic behaviour are explained. The advantages and limitations of the framework are discussed, and future research directions are laid out.